The invention relates to a self-extinguishing expansion electrical circuit breaker having a sealed enclosure filled with a high dielectric strength insulating gas, and housing one or more pole-units, each pole-unit comprising:
a first extinguishing chamber designed to store insulating gas heated by an arc; PA1 a pair of contacts with relative axial translation movement comprising separable arcing contacts bounding a breaking gap in the first chamber; PA1 a tubular gas outflow duct, arranged inside at least one of the contacts to make the first extinguishing chamber communicate with the remaining volume of the enclosure forming the second gas expansion chamber.
A circuit breaker of this kind is described in the European patent document EP-A-298,809 the corresponding U.S. Patent is U.S. Pat. No. 4,900,882.
Tests have shown that the gas outflow via the ducts of the tubular contacts to the second expansion chamber can generate an ordered gas outflow, with spiral movement along the axis. The resulting Vortex effect then causes a variation of the gas density with the formation of a central zone of low density located in the vicinity of the axis of each tubular contact. This results in a decrease of the dielectric withstand, with risks of arc restriking inside the arcing contacts.
The object of the invention consists in improving the dielectric withstand of a circuit breaker with self-extinguishing expansion of the insulating gas.